Check your overflow from time to time, at least more frequently than me. My RBTA splits every so often and the other day I was cleaning my overflow and found a small, pale rbta back there - very little light makes it in there. I assume it was from a spilt I didn't notice and it wandered through the overflow.
I have it back in the main display and it is doing fine. I'm just feeding it more than the others and have it high up on the rocks trying to get the zooxanthellae back up to norm.